Single Phase Synthesis; Neutron Diffraction and Dielectric Studies on 0.6PbFe0.5Nb0.5O3-0.4BiFeO3 Multiferroic

0.6Pb(Fe0.5Nb0.5)O3-0.4BiFeO3 (0.6PFN-0.4BFO) multiferroic solid solution was synthesized by single step solid state reaction method. The optimized synthesis parameters for 0.6PFN-0.4BFO multiferroic was calcination at 700 °C /2 hr and sintering at 800 °C /3 hr. Single phase was confirmed though room temperature X-ray Diffraction (XRD) and room temperature Neutron Diffraction (ND). XRD and ND data were well fitted with monoclinic structure with Cm space group. The magnetic structure was refined using the propagation vector k = (0.5; 0.5; 0.5) and the structure was found to be G-type antiferromagnetic. The dielectric constant and loss tangent of 0.6PFN-0.4BFO shows the frequency and temperature dependent nature. Loss tangent exhibits the thermally dependent relaxation peaks. 0.6PFN-0.4BFO is a potential candidate for above room temperature applications

Synthesis and Studies of High-Temperature Electrical Properties of Pb0.8Bi0.2Fe0.734W0.266O3 Solid Solution

The Pb0.8Bi0.2(Fe0.734W0.266)O3 (PBFW) high temperature ceramic has been successfully synthesized by the modified columbite method. The phase purity was confirmed by the room temperature X-ray diffraction measurement and it confirms the formation of cubic structure with Pm-3m space group. The lattice parameters were obtained from the Rietveld refinement technique; with a = b = c = 3.9750 Å. From the Scanning Electron Micrograph; the average grain size were measured about 1 µm and the Gaussian distribution showed uniform distribution of particles with small amount of porous nature. Temperature-dependent ferroelectric (P-E loop) measurement confirms the presence of polar Nanodomains along with leaky behavior owing to the conducting nature of the sample. A detailed study of frequency dependent permittivity and loss tanδ evidenced the Maxwell-Wagner type of polarization. The Non-Debye type of relaxation in the PBFW was confirmed by analyzing the Impedance spectra and fitting the Kohlraush-Williams-Watt function to the electric modulus at few selected temperatures. The impedance spectra reveal that the grain boundaries are more resistive than grains. By fitting the Johnscher's power law to the ac conductivity and from the ‘n' value; we conclude that the system has Correlated Barrier Hopping (CBH) conduction mechanis

Lepton Dipole Moments and Rare Decays in the CP-violating MSSM with Nonuniversal Soft-Supersymmetry Breaking

We investigate the muon anomalous magnetic dipole moment (MDM), the muon electric dipole moment (EDM) and the lepton-flavour-violating decays of the $\tau-$lepton, $\tau \to \mu \gamma$ and $\tau\to 3\mu$, in the CP-violating Minimal Supersymmetric Standard Model (MSSM) with nonuniversal soft-supersymmetry breaking. We evaluate numerically the muon EDM and the branching ratios $B(\tau \to \mu\gamma)$ and $B(\tau \to 3\mu)$, after taking into account the experimental constraints from the electron EDM and muon MDM. Upon imposition of the experimental limits on our theoretical predictions for the aforementioned branching ratios and the muon MDM, we obtain an upper bound of about $10^{-23} e\cdot cm$ on the muon EDM which lies well within the explorable reach of the proposed experiment at BNL.Comment: Latex, 26 pages, 8 figures, accepted for publication in Phys. Rev.

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250 mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap different from that of Sn, and a zero-bias conductance peak growing up at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.Comment: 7 pages, 8 figure

Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV

PHENIX has measured the centrality dependence of charged hadron p_T spectra from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction of the contribution from hard scattering to high p_T hadron production. For central collisions the yield at high p_T is shown to be suppressed compared to binary nucleon-nucleon collision scaling of p+p data. This suppression is monotonically increasing with centrality, but most of the change occurs below 30% centrality, i.e. for collisions with less than about 140 participating nucleons. The observed p_T and centrality dependence is consistent with the particle production predicted by models including hard scattering and subsequent energy loss of the scattered partons in the dense matter created in the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to Phys. Lett. B. Revised to address referee concerns. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm

Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Heavy Quarks and Heavy Quarkonia as Tests of Thermalization

We present here a brief summary of new results on heavy quarks and heavy quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma Thermalization" Workshop in Vienna, Austria in August 2005, directly following the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop (Vienna August 2005) Proceeding

Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV

The invariant differential cross section for inclusive electron production in p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4 <= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Nuclear Modification of Electron Spectra and Implications for Heavy Quark Energy Loss in Au+Au Collisions at sqrt(s_NN)=200 GeV

The PHENIX experiment has measured mid-rapidity transverse momentum spectra (0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were removed. The resulting non-photonic electron spectra are primarily due to the semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to non-photonic electrons in p+p collisions. A significant suppression of electrons at high p_T is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.Comment: 330 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm